1. Field of the Invention
The present invention relates to a roller for supporting or driving flat products or sheets, in particular for a continuous treating installation.
In the course of the manufacture of the sheet, the latter is heat treated in a continuous annealing furnace after the rolling operations. The furnace, which has a length which may be as much as or even exceed 130 m, suitably heats the sheet passing through the furnace. This sheet is driven inside the furnace by hollow rollers. At the end of or during the heating, a little before the exit of the furnace, there is provided in the latter a device for measuring the temperature of the sheet for controlling the heating of the furnace.
2. Discussion of the Related Art
It is known to take the temperature of the sheet by means of a thermocouple disposed in a hollow driving roller placed inside the furnace. For this purpose, it is known to place the hot junction of the thermocouple in a blind hole in a block of material identical to that of the roller and to fix this block, by force or by soldering or welding in an opening provided through the wall of the roller in a region where its outer surface cooperates with the sheet by contact. In this way, the hot junction of the thermocouple is fixed in a block embedded in a wall of the roller in the vicinity of the outer surface of the roller. The remaining part of the thermocouple comprising the wires of the latter extends inside the roller The small thickness of material separating the hot junction of the thermocouple from the sheet permits assimilating the temperature taken by the thermocouple to that of the sheet.
However, when the roller has been assembled and placed in position in the furnace, it is impossible for an operator to have access to the interior of the roller. Consequently, in the event of failure of the thermocouple, as the latter is fixed inside the roller, it cannot be replaced without dismantling the roller.
Further, the opening cut in the wall of the roller and the fixing of the block of material containing the hot junction of the thermocouple in the opening create in this wall stresses which may form cracks and defects on the outer surface of the roller.